AbuseIPDB scores for clients that committed an offence, within a daily budget (closes #105)

With SWWAF_ABUSEIPDB_KEY set, a client whose history counts an offence
(a broken limit, a ban rule's match or a block rule's refusal, counted
by kind) is checked in the background, at most
SWWAF_ABUSEIPDB_DAILY_BUDGET checks a day, the count kept in
reputation.json. A client, an IPv4 address or an IPv6 /64, is checked by
the address it sent from, and its score serves all its addresses. A
score at or over SWWAF_ABUSEIPDB_MIN_SCORE is a hit for
SWWAF_REPUTATION_ACTION, logged as abuseipdb and alerted with its score.
A failure or the used-up budget gives no score and raises
source_failure. The key goes only in the Key header.

Judgement call: the budget's day is UTC; AbuseIPDB documents no reset time.
Judgement call: each check sent spends budget; a minute's pause after a failure.

Model: opus-5-5

internal/proxy/proxy.go

@@ -59,6 +59,9 @@ type Params struct {
 	// GeoJSURL is where clients' AS numbers and countries are looked up
 	// while SWWAF_LOOKUP_SOURCE is geojs, normally lookup.URL.
 	GeoJSURL string
+	// AbuseIPDBURL is where clients are checked with AbuseIPDB while
+	// SWWAF_ABUSEIPDB_KEY is set, normally reputation.AbuseIPDBURL.
+	AbuseIPDBURL string
 	// LookupFile is the lookup database they are looked up in while
 	// SWWAF_LOOKUP_SOURCE is file, and nil otherwise.
 	LookupFile *lookup.File
@@ -71,15 +74,17 @@ type Params struct {
 	Rules *rules.Files
 	// Alerts receive the alert for each ban the proxy makes or makes
 	// permanent, for each count over an anomaly threshold, for each request
-	// whose client a blocklist or a DNSBL zone lists, and for GeoJS failing,
-	// a fetch of a list failing or a query to a DNSBL zone failing.
+	// whose client a blocklist, a DNSBL zone or AbuseIPDB lists, and for
+	// GeoJS failing, a fetch of a list failing, a query to a DNSBL zone or
+	// a check with AbuseIPDB failing, or the day's AbuseIPDB checks used up.
 	Alerts *alerts.Queue
 }
 
 // Server is the server smallwebwaf runs, with the parts of the proxy
 // whose state the state files keep, the lookup database, nil unless
 // SWWAF_LOOKUP_SOURCE is file, the lists fetched from URLs, which its Run
-// fetches, the DNSBL zones' verdicts, and the metrics.
+// fetches, the DNSBL zones' verdicts, AbuseIPDB's scores and checks
+// spent, and the metrics.
 type Server struct {
 	*http.Server
 
@@ -90,6 +95,7 @@ type Server struct {
 	LookupFile *lookup.File
 	Lists      *reputation.Lists
 	DNSBL      *reputation.DNSBL
+	AbuseIPDB  *reputation.AbuseIPDB
 	Metrics    *metrics.Metrics
 }
 
@@ -102,7 +108,7 @@ type Server struct {
 func New(params Params) *Server {
 	errorLog := slog.NewLogLogger(params.ProcessLog.Handler(), slog.LevelWarn)
 	m := metrics.New(params.Config.MetricsTopN, params.Config.InstanceName)
-	lists, dnsbl := newReputation(params)
+	lists, dnsbl, abuseIPDB := newReputation(params, m)
 	h := &handler{
 		config:     params.Config,
 		requestLog: params.RequestLog,
@@ -140,6 +146,7 @@ func New(params Params) *Server {
 		lookupFile: params.LookupFile,
 		lists:      lists,
 		dnsbl:      dnsbl,
+		abuseIPDB:  abuseIPDB,
 		rules:      params.Rules,
 		alerts:     params.Alerts,
 	}
@@ -159,7 +166,6 @@ func New(params Params) *Server {
 	})
 	m.AddBansAndClients(h.ledger, h.limiter, params.Now)
 	m.AddRules(params.Rules)
-	m.AddReputation(h.lists, h.dnsbl)
 
 	return &Server{
 		Server: &http.Server{
@@ -181,14 +187,18 @@ func New(params Params) *Server {
 		LookupFile: h.lookupFile,
 		Lists:      h.lists,
 		DNSBL:      h.dnsbl,
+		AbuseIPDB:  h.abuseIPDB,
 		Metrics:    m,
 	}
 }
 
-// newReputation returns the lists fetched from URLs and the DNSBL zones'
-// verdicts, as the settings in params name them, with none fetched or
-// asked for yet.
-func newReputation(params Params) (*reputation.Lists, *reputation.DNSBL) {
+// newReputation returns the lists fetched from URLs, the DNSBL zones'
+// verdicts and AbuseIPDB's scores, as the settings in params name them,
+// with none fetched, asked for or checked yet, and adds their metrics to
+// m, AbuseIPDB's while SWWAF_ABUSEIPDB_KEY is set.
+func newReputation(
+	params Params, m *metrics.Metrics,
+) (*reputation.Lists, *reputation.DNSBL, *reputation.AbuseIPDB) {
 	cfg := params.Config
 	lists := reputation.New(reputation.Params{
 		BlocklistURLs: cfg.BlocklistURLs, Refresh: cfg.BlocklistRefresh,
@@ -200,8 +210,20 @@ func newReputation(params Params) (*reputation.Lists, *reputation.DNSBL) {
 		Timeout: cfg.ReputationTimeout, Now: params.Now, ProcessLog: params.ProcessLog,
 		Alerts: params.Alerts,
 	})
+	abuseIPDB := reputation.NewAbuseIPDB(reputation.AbuseIPDBParams{
+		URL: params.AbuseIPDBURL, Key: cfg.AbuseIPDBKey, MinScore: cfg.AbuseIPDBMinScore,
+		DailyBudget: cfg.AbuseIPDBDailyBudget, CacheTTL: cfg.ReputationCacheTTL,
+		Timeout: cfg.ReputationTimeout, Now: params.Now, ProcessLog: params.ProcessLog,
+		Alerts: params.Alerts,
+	})
 
-	return lists, dnsbl
+	m.AddReputation(lists, dnsbl)
+
+	if cfg.AbuseIPDBKey != "" {
+		m.AddAbuseIPDB(abuseIPDB)
+	}
+
+	return lists, dnsbl, abuseIPDB
 }
 
 // handler is the proxy. It holds what every request shares; what belongs
@@ -221,6 +243,7 @@ type handler struct {
 	lookupFile *lookup.File
 	lists      *reputation.Lists
 	dnsbl      *reputation.DNSBL
+	abuseIPDB  *reputation.AbuseIPDB
 	rules      *rules.Files
 	alerts     *alerts.Queue
 }